U.S. patent application number 12/411996 was filed with the patent office on 2009-07-16 for information transmitting method and information transmitting system.
Invention is credited to Shiro MAZAWA, Yosuke TAKAHASHI, Daigo TAKAYANAGI, Akihiko YOSHIDA.
Application Number | 20090180419 12/411996 |
Document ID | / |
Family ID | 37030863 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090180419 |
Kind Code |
A1 |
TAKAYANAGI; Daigo ; et
al. |
July 16, 2009 |
INFORMATION TRANSMITTING METHOD AND INFORMATION TRANSMITTING
SYSTEM
Abstract
An information transmitting method including; determining, on a
basis of a packet error rate from a master station to slave
stations, a number of times of multicast transmission in accordance
with an expected value of a number of slave stations that transmit
a retransmission request, an expected value of a number of
retransmitted packets responding to the retransmission request, or
a probability that the slave stations receive all packets forming
information; notifying determined number of times of multicast
transmission to the slave stations; and transmitting, to plural
slave stations in multicast, same information formed of plural
packets the determined times of multicast transmission.
Inventors: |
TAKAYANAGI; Daigo;
(Yokohama, JP) ; MAZAWA; Shiro; (Fujisawa, JP)
; TAKAHASHI; Yosuke; (Yokohama, JP) ; YOSHIDA;
Akihiko; (Yokohama, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
37030863 |
Appl. No.: |
12/411996 |
Filed: |
March 26, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11353173 |
Feb 14, 2006 |
|
|
|
12411996 |
|
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Current U.S.
Class: |
370/312 |
Current CPC
Class: |
H04L 12/1868 20130101;
H04L 2001/0093 20130101; H04W 48/08 20130101; H04W 8/26 20130101;
H04L 1/1867 20130101; H04L 12/189 20130101; H04W 4/06 20130101 |
Class at
Publication: |
370/312 |
International
Class: |
H04H 20/71 20080101
H04H020/71 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2005 |
JP |
2005-097759 |
Claims
1. An information transmitting method including; determining, on a
basis of a packet error rate from a master station to slave
stations, a number of times of multicast transmission in accordance
with an expected value of a number of slave stations that transmit
a retransmission request, an expected value of a number of
retransmitted packets responding to the retransmission request, or
a probability that the slave stations receive all packets forming
information; notifying determined number of times of multicast
transmission to the slave stations; and transmitting, to plural
slave stations in multicast, same information formed of plural
packets the determined times of multicast transmission.
2. The information transmitting method according to claim 1,
wherein in the determining, the number of times of multicast
transmission is determined for plural areas of base stations
communicating with the slave stations, and in the transmitting to
the plural slave stations, the same information is transmitted to
the slave stations in the respective areas, the determined times of
multicast transmission in the respective areas.
3. The information transmitting method according to claim 1,
wherein, in the determining, the number of times of multicast
transmission is determined such that an expected value of the
number of slave stations that transmit retransmission requests is
equal to or smaller than a predetermined ratio of a total number of
slave stations managed by the base stations.
4. The information transmitting method according to claim 3,
wherein, in the determining, a minimum integer of a value x
obtained in accordance with Expression below is set as the number
of times of multicast transmission: x.gtoreq.log.sub.P(1- N{square
root over (1-C.sub.1)}) Expression 1 where x is the number of times
of multicast transmission, P is a packet error rate, N is a number
of packets of transmitted information, and C.sub.1 is a coefficient
set in advance.
5. The information transmitting method according to claim 1,
wherein, in the determining, the number of times of multicast
transmission is determined such that the expected value of the
number of retransmitted packets responding to a retransmission
request from one slave station is equal to or smaller than a
predetermined ratio of the number of packets of transmitted
information.
6. The information transmitting method according to claim 5,
wherein, in the determining, a minimum integer of a value x
obtained in accordance with Expression below is set as the number
of times of multicast transmission: x.gtoreq.log.sub.PC.sub.2
Expression 2 where x is the number of times of multicast
transmission, P is a packet error rate, and C.sub.2 is a
coefficient set in advance.
7. The information transmitting method according to claim 1,
wherein, in the determining, the number of times of multicast
transmission is determined such that the probability that slave
stations, which receive information the notified times of multicast
transmission, receive all packets of information to be received is
equal to or larger than a probability set in advance.
8. The information transmitting method according to claim 7,
wherein, in the determining, the number of times of multicast
transmission is determined in accordance with Expression below:
x=log.sub.P(1- NM {square root over (C.sub.3)}) Expression 3 where
x is the number of times of multicast transmission, P is a packet
error rate, N is a number of packets of transmitted information, M
is a number of slave stations, and C.sub.3 is a target probability
value set in advance.
9. A master station comprising: a transmitting unit for
transmitting information to slave stations; a receiving unit for
receiving information from the slave stations; and a control unit
that controls information transmission to the slave stations,
wherein the control unit; determines, on a basis of a packet error
rate from the master station to the slave stations, a number of
times of multicast transmission in accordance with an expected
value of a number of slave stations that transmit retransmission
requests, an expected value of a number of retransmitted packets
responding to the retransmission requests, or a probability that
the slave stations receive all packets forming information;
notifies determined number of times of multicast transmission to
the slave stations via the transmitting unit; and transmits same
information formed of plural packets to plural slave stations via
the transmitting unit in multicast, the determined times of
multicast transmission.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a continuation of U.S. application Ser. No.
11/353,173, filed Feb. 14, 2006. This application relates to and
claims priority from Japanese Patent Application No. 2005-097759,
filed on Mar. 30, 2005. The entirety of the contents and subject
matter of all of the above is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an information transmitting
method and an information transmitting system, and, in particular
to an information transmitting method and an information
transmitting system for surely transmitting one piece of
information to plural terminals (such a system will be hereinafter
referred to as broadcast download) in a communication system that
makes both multicast transmission and unicast transmission
possible.
[0003] As information transmission, there are, for example, unicast
transmission for transmitting a packet to separate addresses of
respective terminals and multicast transmission for transmitting a
packet to an address common to plural terminals. The unicast
transmission has an advantage that it is possible to separately
retransmit a packet to a terminal that fails to receive the packet.
The unicast transmission has a disadvantage that, even when one
piece of information is transmitted to plural terminals, a
transmission capacity proportional to the number of receiving
terminals is consumed. On the other hand, the multicast
transmission has an advantage that, when one piece of information
is transmitted to plural terminals, only a transmission capacity
for one terminal is consumed. The multicast transmission has a
disadvantage that it is impossible to separately retransmit a
packet to a terminal that fails to receive the packet.
[0004] As a technique for realizing certainty of transmission, for
example, a technology described in JP-A-2003-273925 is known. In
the technique described in JP-A-2003-273925, for example, a master
station sends a packet in multicast once and, then, waits for
delivery confirmation information from slave stations. When the
number of slave stations from which the delivery confirmation
information is not obtained is larger than a threshold value, the
master station retransmits the packet in multicast. When the number
of such slave stations is smaller than the threshold value, the
master station retransmits the packet in unicast. Consequently,
certainty of transmission is realized.
[0005] A system for allowing a reception side to normally receive
an abandoned packet without issuing a retransmission request for
the abandoned packet is also known (e.g., US2004/0117498 A1).
[0006] In the broadcast download, for example, on the premise that
information is surely transmitted, it is an object to minimize
consumption of a transmission capacity and quickly perform
transmission.
[0007] In the technique in which a master station transmits a
packet in multicast and slave stations do not transmit delivery
confirmation information or retransmission requests, it is
impossible to guarantee that information is surely communicated to
the respective slave stations. When the download broadcast is
performed only by unicast, since a transmission capacity
proportional to the number of slave stations is consumed, the
transmission capacity is wastefully consumed compared with
transmission by multicast. In the case of time division multiplex,
time required for transmission increases as the number of slave
stations increases.
[0008] On the other hand, when only first transmission is performed
by multicast and retransmission is performed by unicast, in
particular, when there are a large number of retransmission
requests, at a stage of first retransmission, a problem same as the
problem of the broadcast download performed only by unicast.
[0009] As in JP-A-2003-273925, when multicast and unicast is
switched on a basis of delivery confirmation information from the
slave stations every time transmission is performed, since the
delivery confirmation information is transmitted from the slave
stations every time, an up transmission capacity is suppressed. For
example, since delivery confirmation information generated by the
slave stations increases in proportion to the number of slave
stations every time the master station transmits a packet, when
there are a large number of slave station, an up transmission
capacity is suppressed. Moreover, since it is necessary to provide
time for waiting for delivery confirmation information, quick
transmission of information is hindered. For example, since it is
necessary to provide time for waiting for delivery confirmation
information from the slave stations every time the master station
transmits a packet, efficiency is low in terms of quickness.
SUMMARY OF THE INVENTION
[0010] The invention has been devised in view of the problems and
it is an object of the invention to provide an information
transmitting method and an information transmitting system for
performing transmission surely and quickly by controlling
consumption of a transmission capacity in broadcast download. It is
another object of the invention to control an up transmission
capacity and reduce the number of times of multicast transmission
as much as possible. It is still another object of the invention to
reduce time required for surely transmitting information. It is
still another object of the invention to provide a method of
determining the number of times of multicast transmission.
[0011] In order to solve the problem, in the invention, in order to
surely and quickly perform transmission without wastefully
consuming a transmission capacity in the broadcast download, first,
transmission is started in multicast and, after a several times of
multicast, transmission is switched to unicast. As a characteristic
of the invention, for example, first, a master station transmits
identical information in multicast continuously for a plural times,
then, receives a retransmission request from a slave station for
the first time, and, after that, solely perform retransmission in
unicast. The slave station indicates, for example, a radio
terminal. The master station indicates, for example, a radio base
station or an apparatus such as PDSN.
[0012] As another characteristic of the invention, (1) a method of
determining an expected value of the number of slave stations that
request retransmission to be equal to or smaller than a
predetermined ratio of a total number of slave stations, (2) a
method of determining an expected value of the number of packets
requested to be retransmitted per one slave station to be equal to
or smaller than a predetermined ratio of the number of service data
packets, or (3) a method of determining a probability that slave
stations after receiving information in multicast a determined
number of times have completed reception of all pieces of
information to be a predetermined probability is used as a method
of determining the number of times of multicast transmission.
[0013] An information transmitting system of the invention is, for
example, an information transmitting system in which a master
station transmits identical information to plural slave stations.
As a characteristic of the information transmitting system, first,
the master station transmits the information to the slave stations
in multicast continuously for a plural number of times. The slave
stations receive the information through the continuous plural
times of multicast. When there is a lack in the information, a
slave station transmits a retransmission request to the master
station. The master station retransmits the information to the
slave station, which transmits the retransmission request, in
unicast. The slave station, which transmits the retransmission
request, receives the information retransmitted from the master
station, which receives the retransmission requests, in
unicast.
[0014] In the information transmitting system, it is possible to
notify, before the master station performs multicast transmission,
the slave stations of the number of times of the multicast
transmission. In the information transmitting system as a method
with which the master station determines the number of times of
multicast transmission, it is possible to use a method of
determining an expected value of the number of slave stations that
request retransmission by unicast to be equal to or smaller than a
predetermined ratio of a total number of slave stations.
[0015] In the information transmitting system, as a method with
which the master station determines the number of times of
multicast transmission, it is possible to use a method of
determining an expected value of the number of retransmitted
packets responding to retransmission requests by unicast of one
slave station to be equal to or smaller than a predetermined ratio
of the number of service data packets. In the information
transmitting system, as a method with which the master station
determines the number of times of multicast transmission, it is
possible to use a method of determining a probability that slave
stations after receiving multicast transmission of a determined
number of times have completed reception of all pieces of
information to be a predetermined probability.
[0016] A master station of the invention is, for example, a master
station of an information transmitting system in which the master
station transmits identical information to plural slave station. As
a characteristic, the master station has a function of transmitting
identical information to the slave stations in multicast and
retransmitting the information to a slave station, which requests
retransmission, in unicast.
[0017] A slave station of the invention is, for example, a slave
station of an information transmitting system in which a master
station transmits identical information to plural stations. As a
characteristic, the slave station has a function of receiving the
information from the master station in multicast and, when there is
a lack in the information, transmitting retransmission requests to
the master station, and receiving retransmitted information from
the master station, which receives the retransmission requests, in
unicast.
[0018] The master station can have a function of notifying, before
performing multicast transmission, the slave stations of the number
of times of the multicast transmission. The master station can have
a function of determining the number of times of transmission in
multicast according to a packet error rate, the number of slave
stations, and the number of service data packets. The slave
stations can have a function of receiving, in multicast, the
information equivalent to the number of times of multicast
transmission notified from the master station, abandoning
information received redundantly, and holding one piece of
information.
[0019] According to first solving meaning of the invention, there
is provided an information transmitting method including:
[0020] determining, on a basis of a packet error rate from a master
station to slave stations, a number of times of multicast
transmission in accordance with an expected value of a number of
slave stations that transmit a retransmission request, an expected
value of a number of retransmitted packets responding to the
retransmission request, or a probability that the slave stations
receive all packets forming information;
[0021] notifying the determined number of times of multicast
transmission to the slave stations;
[0022] transmitting, to plural slave stations in multicast, same
information formed of plural packets the determined times of
multicast transmission;
[0023] connecting unicast connection to a slave station that
identifies a lacking packet after receiving information the
notified times of multicast transmission;
[0024] receiving, from the slave station that receives information
in multicast, a retransmission request including an identifier of
the lacking packet among packets forming the information by the
unicast connection; and
[0025] retransmitting a packet corresponding to the identifier of
the packet to the slave station by the unicast connection.
[0026] According to second solving means of the invention, there is
provided a master station comprising:
[0027] a transmitting unit for transmitting information to slave
stations;
[0028] a receiving unit for receiving information from the slave
stations; and
[0029] a control unit that controls information transmission to the
slave stations,
[0030] wherein the control unit:
[0031] determines, on a basis of a packet error rate from the
master station to the slave stations, a number of times of
multicast transmission in accordance with an expected value of a
number of slave stations that transmit retransmission requests, an
expected value of a number of retransmitted packets responding to
the retransmission requests, or a probability that the slave
stations receive all packets forming information,
[0032] notifies the determined number of times of multicast
transmission to the slave stations via the transmitting unit,
[0033] transmits same information formed of plural packets to
plural slave stations via the transmitting unit in multicast, the
determined times of multicast transmission,
[0034] connects unicast connection to a slave station that
identifies a lacking packet after receiving information, the
notified number of times of multicast transmission,
[0035] receives, from the slave station that receives information
in multicast, a retransmission request including an identifier of
the lacking packet among packets forming the information by the
unicast connection via the receiving unit; and
[0036] retransmits a packet corresponding to the identifier of the
packet to the slave station by the unicast connection.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] In the accompanying drawings:
[0038] FIG. 1 is a diagram showing an example of an information
transmitting system to which the invention is applied;
[0039] FIG. 2 is a diagram showing a communication procedure of the
invention on a basis of the example of the radio information
transmitting system in FIG. 1;
[0040] FIG. 3 is a block diagram showing a functional constitution
of a radio terminal;
[0041] FIG. 4 is a block diagram showing a functional constitution
of a radio base station;
[0042] FIG. 5 is a block diagram showing a functional constitution
of a radio network control device;
[0043] FIG. 6 is a block diagram showing a functional constitution
of a PDSN;
[0044] FIG. 7 is a block diagram showing a functional constitution
of a broadcast download service control device;
[0045] FIG. 8 is a block diagram showing a functional constitution
of a data server;
[0046] FIG. 9 is a format diagram of a table in the radio base
station;
[0047] FIG. 10 is a format diagram of the table in the radio base
station;
[0048] FIG. 11 is a format diagram of a multicast information table
in a PDSN 14;
[0049] FIG. 12 is a format diagram of a service information table
in a broadcast download service control device 15;
[0050] FIGS. 13A and 13B are flowchart of detailed processing of
the radio terminal;
[0051] FIG. 14 is a flowchart of detailed processing of the radio
terminal;
[0052] FIGS. 15A and 15B are flowcharts of detailed processing of
the radio base station;
[0053] FIGS. 16A and 16B are flowcharts of detailed processing of
the radio base station;
[0054] FIG. 17 is a flowchart of processing at the time when the
radio network control device receives a radio network control
device service implementation request;
[0055] FIGS. 18A and 18B are flowcharts of detailed processing of
the PDSN;
[0056] FIGS. 19A to 19C are flowcharts of detailed processing of
the PDSN;
[0057] FIGS. 20A and 20B are flowcharts of detailed processing of
the broadcast download service control device;
[0058] FIGS. 21A and 21B are flowcharts of detailed processing of
the broadcast download service control device; and
[0059] FIG. 22 is a flowchart of processing at the time when the
data server receives a service data request.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hardware Configuration
[0060] An example of an radio information transmitting system to
which the invention is applied is shown in FIG. 1. This system
comprises, for example, radio base stations 12, a radio network
control device 13, a Packet Data Serving Node (PDSN) 14, a
broadcast download service control device 15, and a data server 16.
The radio base stations 12 (12-1 and 12-2) communicate with plural
radio terminals 20 (21a to 22c). Communication may be performed by
wire other than radio.
[0061] Service data for broadcast download is stored in the data
server 16. Service information such as a service area and a service
start time is stored in the service control device 15 for each
service data. The service control device 15 controls a service. The
PDSN 14 processes service data from the data server 16 in an IP
network into a service packet for a radio network and transmits the
service packet to the base stations 12 in the service area. The
radio network control device 13 monitors and controls the radio
base stations 12 via the radio network.
[0062] For example, one of the radio base stations 12 has
transmission areas (areas 1a to 1c or areas 2a to 2c) in three
directions and performs communication with the radio terminals 20
for each of the areas in time division multiplex. For example, the
radio base stations 12 can transmit, in multicast, service data and
data indicating the number of times of transmission for each of the
areas. For example, the radio base station 12-1 has transmission
areas 1a, 1b, and 1c and the radio base station 12-2 has
transmission areas 2a, 2b, and 2c. For example, the radio terminals
21a-1 to 21a-i are in the area 1a, the radio terminals 21b-1 to
21b-j are in the area 1b, and the radio terminals 21c-1 to 21c-k
are in the area 1c. Similarly, for example, the radio terminals
22a-1 to 22a-1 are in the area 2a, the radio terminals 22b-1 to
22b-m are in the area 2b, and the radio terminals 22c-1 to 22c-n
are in the area 2c.
[0063] In unicast communication, when a packet reception error
occurs, the radio terminals 20 transmit retransmission requests to
the radio base stations 12. The radio base stations 12 retransmit
packets to the respective radio terminals. In multicast
communication, the radio base stations 12 add a strong error
correction code to service data and guarantee that a packet error
rate in an area is equal to or lower than a value P set in
advance.
[0064] Functional constitutions of the respective nodes will be
explained.
[0065] FIG. 3 is a block diagram showing a functional constitution
of the radio terminal 20. The radio terminal 20 includes a
receiving unit 31, a transmitting unit 32, an error correcting unit
33, a control unit 34, a decryption key storing unit 35, a service
data storing unit 36, and a number of times of multicast
transmission storing unit 37. In FIG. 3, the storing units 35 to 37
may be constituted by one storing unit or may be constituted by
plural storing units.
[0066] The receiving unit 31 receives information transmitted from
the radio base station 12 by radio. The transmitting unit 32
transmits information to the radio base station 12 by radio. The
error correcting unit 33 subjects information received by the
receiving unit 31 to error correction. The control unit 34 performs
control according to a type of information received by the
receiving unit 31.
[0067] The control by the control unit 34 will be explained. FIG.
13A is a flowchart of control at the time when information received
by the receiving unit 31 is a decryption key from the broadcast
download service control device 15 (202 in FIG. 2). When the
information received by the receiving unit 31 is the decryption key
from the broadcast download service control device 15, the control
unit 34 stores the decryption key in the decryption key storing
unit 35.
[0068] FIG. 13B is a flowchart of control at the time when
information received by the receiving unit 31 is a number of times
of multicast transmission notice from the radio base station 12
(207 in FIG. 2). When the information received by the receiving
unit 31 is the number of times of multicast transmission notice
from the radio base station 12, the control unit 34 stores the
number of times of multicast transmission in the number of times of
multicast transmission storing unit 37.
[0069] FIG. 14 is a flowchart of control at the time when
information received by the receiving unit 31 is service data from
the radio base station 12 (214, 216, and 218 in FIG. 2). When the
information received by the receiving unit 31 is the service data
from the radio base station 12, the control unit 34 stores the
service data in the service data storing unit 36. In that case,
when the packet received has already been received, it is possible
to abandon the received packet. When the service data is received
the number of times stored in the number of multicast transmission
storing unit 37, the control unit 34 transmits a retransmission
request for a lacking data.
[0070] FIG. 4 is a block diagram showing a functional constitution
of the radio base station 12. The radio base station 12 includes,
for example, a radio network side receiving unit 401, a radio
network side transmitting unit 402, a service data information
storing unit 403, a number of times of multicast transmission
storing unit 404, a number of terminals managing unit 405, a
service data temporarily storing unit 406, a control unit 407, an
error correction code adding unit 408, a terminal side transmitting
unit 409, and a terminal side receiving unit 410. The service data
information storing unit 403, the number of times of multicast
transmission storing unit 404, and the number of terminals managing
unit 405 may be constituted by one memory or may be constituted by
plural memories.
[0071] The radio network side receiving unit 401 receives
information from a radio network side. The radio network side
transmitting unit 402 transmits information to the radio network
side. The terminal side transmitting unit 409 transmits information
to the radio terminal 20 by radio. The terminal side receiving unit
410 receives information transmitted from the radio terminal 20 by
radio. The error correction code adding unit 408 adds an error
correction code to information transmitted from the terminal side
transmitting unit 409.
[0072] The service data information storing unit 403 manages
service data information according to a service data information
table 421. The number of times of multicast transmission storing
unit 404 manages the number of times of multicast transmission for
each of the areas according to a number of times of multicast
transmission table 422. The number of terminals managing unit 405
manages the number of multicast reception terminals for each of the
areas according to a number of area terminals table 423. Detailed
constitutions of the respective tables are described later. The
service data temporarily storing unit 406 temporarily stores
service data received by the radio network side receiving unit 401
before a transmission time, for example, until the transmission
time comes and the service data is transmitted from the terminal
side transmitting unit 409.
[0073] When the radio network side receiving unit 401 receives
information, the control unit 407 performs control according to a
type of the information received. When a service start time comes,
the control unit 407 performs control corresponding to the service
start time. The control by the control unit 407 will be
explained.
[0074] FIGS. 15A and 15B and FIGS. 16A and 16B are flowcharts
showing detailed processing of the radio base station 12.
[0075] FIG. 15A is a flowchart of control at the time when
information received by the radio network side receiving unit 401
is a radio network service implementation request from the radio
network control device 13 (204 in FIG. 2). When the information
received by the radio network side receiving unit 401 is the radio
network service implementation request from the radio network
control device 13, the control unit 407 transmits a service data
information request to the broadcast download service control
device 15.
[0076] FIG. 15B is a flowchart of control at the time when
information received by the radio network side receiving unit 401
is service data information from the broadcast download service
control device 15 (206 in FIG. 2). When the information received by
the radio network side receiving unit 401 is the service data
information from the broadcast download control device 15, the
control unit 407 stores the service data information in the service
data information storing unit 403. The service data information
table 421 shown in FIG. 9 is created in the service data
information storing unit 403.
[0077] The control unit 407 determines the number of times of
multicast transmission for each of the areas on a basis of the
number of terminals for each of the areas stored in the number of
terminals managing unit 405 and the number of service data packets
stored in the service data information storing unit 403 and/or a
packet error rate and stores the number of times of multicast
transmission in the number of times of multicast transmission
storing unit 404 in association with an identifier of the area. The
number of times of multicast transmission table 422 shown in FIG.
10A is created in the number of times of multicast transmission
storing unit 404. The control unit 407 transmits data indicating
the number of times of multicast transmission corresponding to each
of the areas to the radio terminal 20 in the area. The control unit
407 notifies the PDSN 14 of the largest number of times of
transmission among the numbers of times of multicast transmission
for respective areas.
[0078] FIG. 16A is a flowchart of control at the time when
information received by the radio network side receiving unit 401
is service data from the PDSN 14 (213, 215, and 217 in FIG. 2).
When the information received by the radio network side receiving
unit 401 is the service data from the PDSN 14, the control unit 407
temporarily stores the service data in the service data temporarily
storing unit 406.
[0079] FIG. 16B is a flowchart of control at the time when the
service start time stored in the service information storing unit
403 comes. When the service start time comes, the control unit 407
transmits service data to the terminal 20 in the respective areas
the number of times of transmission corresponding to the areas
stored in the number of times of multicast transmission storing
unit 404. In this case, it is possible to transmit the service data
in synchronization with a transmission time given to a packet. This
is for the purpose of achieving synchronization among the radio
base stations 12 to make it possible to continue to perform
reception even if the radio terminal 20 moves among the radio base
stations 12 during a service.
[0080] FIG. 5 is a block diagram showing a functional constitution
of the radio network control device 13. The radio network control
device 13 includes, for example, a transmitting unit 51, a
receiving unit 52, and a control unit 53. The transmitting unit 51
transmits radio network control information from the control unit
53 to the radio network. The receiving unit 52 receives service
implementation information from the broadcast download service
control device 15.
[0081] FIG. 17 is a flowchart of processing at the time when the
radio network control device 13 receives a radio network control
device service implementation request. When the receiving unit 52
receives a radio network control device service implementation
request from the broadcast download service control device 15 (203
in FIG. 2), as shown in the flowchart in FIG. 17, the control unit
53 transmits a radio network service implementation request to the
radio base station 12.
[0082] FIG. 6 is a block diagram showing a functional constitution
of the PDSN 14. The PDSN 14 includes, for example, an IP network
side receiving unit 61, an IP network side transmitting unit 62, a
control unit 63, a radio network side transmitting unit 64, a radio
network side receiving unit 65, a multicast information storing
unit 66, and a service data storing unit 67. The multicast
information storing unit 66 and the service data storing unit 67
may be constituted by one memory or may be constituted by plural
memories.
[0083] The IP network side receiving unit 61 receives information
from the IP network. The IP network side transmitting unit 62
transmits information to the IP network. The radio network side
transmitting unit 64 transmits information to the radio network.
The radio network side receiving unit 65 receives information from
the radio network. The multicast information storing unit 66 has a
multicast information table 661. As an example, the number of times
of multicast transmission passed from the control unit 63 is stored
in the multicast information table 661. Details of the table are
described later. The service data storing unit 67 stores service
data passed from the control unit 63.
[0084] The control unit 63 performs control according to a type of
information received by the IP network side receiving unit 61 or
the radio network side receiving unit 65. When time reaches a PDSN
service data transmission start time in the multicast information
table 661 of the multicast information storing unit 66, the control
unit 63 performs control corresponding to the PDSN service data
transmission start time. The control by the control unit 63 will be
explained.
[0085] FIGS. 18A and 18B and FIGS. 19A to 19C are flowcharts
showing detailed processing of the PDSN.
[0086] FIG. 18A is a flowchart of control at the time when
information received from the radio network side receiving unit 65
is a maximum number of times of multicast transmission notice from
the radio base station 12 (208 in FIG. 2). When the information
received by the radio network side receiving unit 65 is the maximum
number of times of multicast transmission notice from the radio
base station 12, the control unit 63 stores an identifier (ID) of
the radio base station 12 that transmits the notice, a service data
number, and the maximum number of times of multicast transmission
notified in the multicast information storing unit 66 in
association with one another. The multicast information table 661
is created in the multicast information storing unit 66. The
control unit 63 transmits a PDSN service data information request
to the broadcast download service control device 15.
[0087] FIG. 18B is a flowchart of control at the time when
information received by the IP network side receiving unit 61 is a
PDSN service data information from the broadcast download control
device 15. When the information received by the IP network side
receiving unit 61 is the PDSN service data information from the
broadcast download control device 15 (210 in FIG. 2), the control
unit 63 stores a PDSN service data transmission start time and
synchronization information included in the PDSN service data
information in the multicast information table 661 in the multicast
information storing unit 66. For example, the control unit 63
stores respective pieces of information in a PDSN service data
transmission start time space and a synchronization information
space corresponding to a data service number included in the PDSN
service data information. In the processing in FIG. 18A, the
control unit 63 may store the identifier, the service data number,
and the maximum number of multicast transmission in an entry same
as an entry in which IDs of the radio base stations 12 are stored.
The control unit 63 transmits a service data request to the data
server 16.
[0088] FIG. 19A is a flowchart of control at the time when the IP
network side receiving unit 61 receives service data (212 in FIG.
2). When the IP network side receiving unit 61 receives the service
data, the control unit 63 stores the service data in the service
data storing unit 67.
[0089] FIG. 19B is a flowchart of control at the time when time
reaches the PDSN service data transmission start time stored in the
multicast information table 661 in the multicast information
storing unit 66. When the time reaches the PDSN service data
transmission start time stored in the multicast information table
661 in the multicast information storing unit 66 first, the control
unit 63 divides the service data stored in the service data storing
unit 67 into packets. The control unit 63 gives sequence numbers
and transmission times in the radio base stations 12 calculated on
a basis of the synchronization information to the respective
packets. The control unit 63 transmits the packets to the
respective base stations in multicast the number of times of
multicast transmission corresponding to the base stations in
accordance with the respective radio base station IDs stored in the
multicast information storing unit 66.
[0090] FIG. 19C is a flowchart of control at the time when the
radio network side receiving unit 65 receives a retransmission
request from the radio terminal 20 (220 and 222 in FIG. 2). When
the radio network side receiving unit 65 receives the
retransmission request from the radio terminal 20, the control unit
63 transmits, in unicast, a requested part in the service data
stored in the service data storing unit 67 to the radio terminal
20.
[0091] FIG. 7 is a block diagram showing a functional constitution
of a broadcast download service control device. The broadcast
download service control device includes, for example, a service
information storing unit 71, a control unit 72, a transmitting unit
73, and a receiving unit 74.
[0092] The service information storing unit 71 has a service
information table 711. The transmitting unit 73 transmits
information passed from the control unit 72. The receiving unit 74
receives, for example, a decryption key request from the radio
terminal 20 and a service data information request from the radio
base station 12. The control unit 72 performs control according to
a type of information received by the receiving unit 74. When time
reaches a radio network control device service start request
transmission time stored in the service information storing unit
71, the control unit 72 performs control corresponding to the radio
network control device service start request transmission time. The
control by the control unit 72 will be explained.
[0093] FIGS. 20A and 20B and FIGS. 21A and 21B are flowcharts of
detailed processing of the broadcast download service control
device.
[0094] FIG. 20A is a flowchart of control at the time when received
information is a decryption key request from the radio terminal 20
(201 in FIG. 2). When the received information is the decryption
key request from the radio terminal 20, the control unit 72 refers
to the service information table 711 stored in the service
information storing unit 71 and transmits a decryption key
corresponding to a service data number included in the request to
the radio terminal 20.
[0095] FIG. 20B is a flowchart of control at the time when time
reaches a radio network control device service implementation
request transmission time stored in the service information storing
unit 71. When the time reaches the radio network control device
service implementation request transmission time stored in the
service information storing unit 71, the control unit 72 includes,
in a radio network control device service implementation request, a
service data number and a service area corresponding to the service
in the service information table 711 in the service information
storing unit 71 and transmits the radio network control device
service implementation request to the radio network control device
13.
[0096] FIG. 21A is a flowchart of control at the time when received
information is a service data information request from the radio
base station 12 (205 in FIG. 2). When the received information is
the service data information request from the radio base station
12, the control unit 72 transmits service data information, which
includes the number of service data packets, a service start time,
and a number of times of multicast transmission determining method
ID corresponding to a requested service data number, and a
coefficient value C.sub.1, C.sub.2, or C.sub.3 corresponding to the
service data number, in the service information table 711 stored in
the service information storing unit 71 to the radio station
12.
[0097] FIG. 21B is a flowchart of control at the time when
information received by the receiving unit 64 is a PDSN service
data information request from the PDSN 14. When the information
received by the receiving unit 64 is the PDSN service data
information request from the PDSN N14, the control unit 72
transmits PDSN service data information, which includes a PDSN
service data transmission start time and synchronization
information corresponding to a requested service data number, in
the service information table 711 stored in the service information
storing unit 71 to the PDSN 14.
[0098] FIG. 8 is a block diagram showing a functional constitution
of the data server 16. The data server 16 includes, for example, a
service data storing unit 81, a control unit 82, a transmitting
unit 83, and a receiving unit 84.
[0099] The service data storing unit 81 stores service data. The
transmitting unit 83 transmits service data passed from the control
unit 82 to the PDSN 14 through the IP network. The receiving unit
84 receives, for example, a service data request from the PDSN 14.
As shown in a flowchart in FIG. 22, when the receiving unit 84
receives a service data request (211 in FIG. 2), the control unit
82 transmits service data corresponding to the service data request
in the service data storing unit 81 to the PDSN 14.
(Table Format)
[0100] FIG. 9 is a format diagram of the service data information
table 421 in the radio base station 12.
[0101] The service data information table 421 includes, for
example, a service data number, a service area, the number of
service data packets, a service start time, a number of times of
multicast transmission determining method ID, and coefficient
values C.sub.1 to C.sub.3.
[0102] The service data number is a number for identifying service
data. An appropriate identifier such as a character or a sign may
be used other than the number. The service area indicates an area
to which the service data is transmitted. The number of service
data packets indicates the number of packets of the service data
indicated by the service data number. The service start time
indicates time when transmission of the service data is started.
The number of times of multicast transmission determining method ID
is an identifier for selecting a method for calculating the number
of times of multicast transmission when there are plural methods of
determining the number of times of multicast transmission. For
example, it is possible to store anyone of 1 to 3 as the ID.
However, the ID is not limited to this. The coefficient values
C.sub.1 to C.sub.3 are coefficient values that are used in
determining the number of times of multicast transmission. It is
possible to store appropriate coefficient values as the coefficient
values according to the number of times of multicast transmission
determining method ID. In an example in FIG. 9, the number of times
of multicast transmission determining method ID is 1 and the
coefficient value C.sub.1 used for calculation by the method is
stored. Fields for C.sub.1 to C.sub.3 do not always have to be
provided. Values of C.sub.1 to C.sub.3 may be appropriately stored
in one or plural fields in which coefficient values are stored.
[0103] FIG. 10A is a format diagram of the number of times of
multicast transmission table 422 in the radio base station 12.
[0104] In the number of times of multicast transmission table 422,
an area and the number of times of multicast transmission are
stored in association with each other for each service data. An
example in FIG. 10A is an example of the number of times of
multicast transmission table 422 concerning service data 1 in the
radio base stations 12-1 and 12-2. In this embodiment, the number
of times of multicast transmission is determined for each of the
areas and stored in this table.
[0105] FIG. 10B is a format diagram of the number of area terminals
table 423 in the radio base station 12. In the number of area
terminals table 423, an area and the number of terminals are stored
in association with each other. The number of terminals indicates,
for example, the number of radio terminals that are capable of
communicating in the respective areas or managed in the respective
areas.
[0106] FIG. 11 is a format diagram of the multicast information
table 661 of the PDSN 14.
[0107] The multicast information table 661 includes a radio base
station ID, a service data number, a PDSN service data transmission
start time, synchronization information, and a maximum number of
times of multicast transmission.
[0108] The radio base station ID is an identifier for identifying
the radio base station 12. The service data number is a number for
identifying service data. The PDSN service data transmission start
time indicates time when transmission of service data from the PDSN
14 to the radio base station 12 is started. The synchronization
information is information for synchronizing multicasted data. The
maximum number of times of multicast transmission indicates the
number of times of multicast transmission to the radio base station
12. A maximum number of times of the numbers of times of multicast
transmission for each of the areas in the radio base station 12 is
stored in the maximum number of times of multicast
transmission.
[0109] FIG. 12 is a format diagram of the service information table
711 in the broadcast download service control device 15.
[0110] The service information table 711 in the broadcast download
service control device 15 includes, for example, a service data
number, the number of service data packets, a service area, a radio
network control device service implementation request transmission
time, a PDSN service data transmission start time, synchronization
information, a service start time, a number of times of multicast
transmission determining method ID, coefficient values C.sub.1,
C.sub.2, and C.sub.3, and a decryption key. These pieces of
information are stored in the service information table 711 in
advance.
[0111] The service data number, the number of service data packets,
the service area, the PDSN service data transmission start time,
the synchronization information, the service start time, the number
of times of multicast transmission determining method ID, and the
coefficient values C.sub.1, C.sub.2, and C.sub.3 are the same as
those described above. Thus, explanations of these pieces of
information are omitted. The radio network control device service
implementation request transmission time indicates time when a
radio network control device service implementation request is
transmitted. The decryption key is a key specified by a service
data number corresponding thereto and is used by the radio terminal
20 to decrypt encrypted service data.
(Operations)
[0112] Operations of the entire system will be explained.
[0113] FIG. 2 is a diagram showing a communication procedure of the
radio information transmitting system in FIG. 1.
[0114] Service data of broadcast download is identified by a
service data number and is encrypted by an encryption key different
from each data. The radio terminal 20 desiring to be offered a
broadcast download service transmits a decryption key request to
the broadcast download service control device 15 before receiving
service data in order to acquire a decryption key for decrypting
encrypted service data (step 201). For example, it is possible to
transmit the decryption key at appropriate timing such as power-on
or input from an input unit. The decryption key request includes a
service data number of a service desired to be offered. It is
possible to store the service data number in the radio terminal 20
in advance. When the broadcast download service control device 15
receives the decryption key request, the broadcast download service
control device 15 refers to the service information table 711 and
transmits a decryption key corresponding to the service data number
included in the decryption key request to the radio terminal 20
(step 202). The radio terminal 20 receives the decryption key and
stores the decryption key in the decryption key storing unit
35.
[0115] When time reaches the radio network control device service
implementation request transmission time in the service information
table 711 stored in the service information storing unit 71, the
broadcast download service control device 15 transmits a radio
network control device service implementation request to the radio
network control device 13 (step 203). The radio base network
control device service implementation request includes a service
data number and a service area corresponding to the radio network
control device service implementation request transmission time in
the service information table 711. In this embodiment, for example,
it is notified that the service data 1 is transmitted in the areas
1b and 1c of the radio base station 12-1 and the area 2a of the
radio base station 12-2.
[0116] The radio network control device 13 having received the
radio network control device service implementation request
transmits a radio network service implementation request to the
radio stations 12-1 and 12-2 corresponding to the service areas
(step 204). The radio network service implementation request
includes a service data number and a service area same as those
included in the radio network control device service implementation
request (step 203). The radio base stations 12-1 and 12-2 receive
the radio network control device service implementation request and
store the service data number and the service area included in the
request in the service data information table 421. When the radio
base stations 12-1 and 12-2 receive the radio network service
implementation request, the radio base stations 12-1 and 12-2
transmits service data information request for requesting
information on service data of the service data number included in
the radio network service implementation request to the broadcast
download service control device 15 (step 205). The service data
information request includes the service data number of service
data information requested.
[0117] When the broadcast download service control device 15
receives the service data information request, the broadcast
download service control device 15 refers to the service
information table 711 and transmits service data information
corresponding to the service data number included in the service
data information request to the radio base stations 12-1 and 12-2
(step 206). The service data information transmitted includes, for
example, the number of service data packets, a service start time,
and an ID (an identifier, for example, a number, a character, or a
sign) for designating a method of determining the number of times
of multicast transmission. The service data information further
includes coefficient values (C.sub.1 to C.sub.3) used for
calculation of the number of times of multicast transmission in
association with the number of times of multicast transmission
determining method ID. The ID for designating a method of
determining the number of times of multicast transmission may be
omitted when one determining method is decided.
[0118] When the determining method is a method of determining the
number of multicast such that the number of retransmission
requesting slave stations is a predetermined ratio of a total
number of slave stations (a first determining method), the service
data information transmitted includes, for example, 1 as the number
of times of multicast transmission determining method ID and a
number of retransmission requesting slave stations expected value
coefficient C.sub.1. When the determining method is a method of
determining the number of times of multicast such that a number of
retransmission requested packets expected value per one slave
station is a predetermined ratio of the number of service data
packet (a second determining method), the service data information
transmitted includes, for example, 2 as the number of times of
multicast transmission determining method ID and a number of
retransmission requested packets expected value coefficient
C.sub.2. When the determining method is a method of determining the
number of times of multicast such that a probability that slave
stations after receiving multicast a determined number of times
have completed reception of all packets is a predetermined
probability (a third determining method), the service data
information transmitted includes, for example, 3 as the number of
times of multicast transmission determining method ID and a target
probability value C.sub.3.
[0119] The radio base stations 12-1 and 12-2 receive the service
data information from the broadcast download control device 15 and
stores the number of service data packets, the service start time,
the number of times of multicast transmission determining method
ID, and the coefficient values included in the service data
information in the service data information table 421. The radio
base stations 12-1 and 12-2 determine the number of times of
multicast transmission for each of the service areas with a method
corresponding to the number of times of multicast transmission
determining method ID.
[0120] The method of determining the number of times of multicast
transmission will be explained.
[0121] First, the first determining method (ID=1) will be
explained. In the first determining method, for example, the number
of times of multicast is determined such that an expected value of
the number of retransmission requesting slave stations for the
first time is equal to or smaller than a predetermined ratio with
respect to the total number of slave stations. When the number of
times of multicast to be calculated is set as x, a packet error
rate is set as P, the number of service data packets is set as N,
the number of radio terminals in an area is set as M, and a number
of first time retransmission requesting slave stations expected
value coefficient is set as C.sub.1, the following Expression is
established.
M{1-(1-P.sup.x).sup.N}.ltoreq.C.sub.1M Expression 1
Therefore, for example, a minimum integer satisfying x of
x.gtoreq.log.sub.P(1- N{square root over (1-C.sub.1)}) Expression
2
is set as the number of times of multicast transmission. It is
possible to calculate the number of times of multicast transmission
for each of the areas.
[0122] More specific processing will be explained. First, the radio
base station 12 (e.g., the control unit 407) reads out a packet
error rate from an appropriate managing unit, storing unit, or the
like that manages the packet error rate P. The radio base station
12 refers to the service data information table 421 and reads out
the number of service data packets N and the coefficient C.sub.1
corresponding to the service data number.
[0123] Subsequently, the radio base station 12 calculates a minimum
integer satisfying Expression 2 and sets the minimum integer as the
number of times of multicast transmission. The radio base station
12 stores the number of times of multicast transmission calculated
in the number of times of multicast transmission table 422 in
association with the area. The radio base station 12 repeats the
processing described above to calculate the number of times of
multicast transmission for all the areas.
[0124] The second determining method (ID=2) will be explained. In
the second determining method, for example, the number of times of
multicast is determined such that the number of first time
retransmission requesting packets per one slave station is equal to
or smaller than a predetermined ratio of the number of service data
packets. When the number of times of multicast to be calculated is
set as x, a packet error rate is set as P, the number of service
data packets is set as N, and a number of first time retransmitted
packets expected value coefficient is set as C.sub.2, the following
Expression is established.
NP.sup.x.ltoreq.C.sub.2N Expression 3
Therefore, for example, a minimum integer satisfying x of
x.gtoreq.log.sub.PC.sub.2 Expression 4
is set as the number of times of multicast transmission.
[0125] More specific processing will be explained. First, the radio
base station 12 (e.g., the control unit 407) reads out the packet
error rate P from an appropriate managing unit, storing unit, or
the like that manages the packet error rate P. The radio base
station 12 refers to the service data information table 421 and
reads out the coefficient C.sub.2 corresponding to the service data
number. Subsequently, the radio base station 12 calculates a
minimum integer satisfying Expression 4 and sets the minimum
integer as the number of times of multicast transmission. The radio
base station 12 stores the number of times of multicast
transmission calculated in the number of times of multicast
transmission table 422 in association with the area. The radio base
station 12 repeats the processing described above to calculate the
number of times of multicast transmission for all the areas.
[0126] The third determining method (ID=3) will be explained. In
the third determining method, for example, the number of times of
multicast is determined such that, for slave stations that have
received multicast a determined number of times, a probability that
reception of all packets of service data corresponding to the slave
stations is completed is a predetermined probability. When the
number of times of multicast to be calculated is set as x, a packet
error rate is set as P, the number of service data packets is set
as N, the number of radio terminals in the area is set as M, and a
target probability value is set as C.sub.3, the following
Expression is established.
(1-p.sup.x).sup.NM=C.sub.3 Expression 5
Therefore, for example, x calculated according to the following
Expression is set as the number of times of multicast
transmission.
x=log.sub.P(1- NM{square root over (C.sub.3)}) Expression 6
As the number of radio terminals M, in the example shown in FIG. 1,
j is used for the area 1b, k is used for the area 1c, and l is used
for the area 2a.
[0127] More specific processing will be explained. First, the radio
base station 12 (e.g., the control unit 407) reads out a packet
error rate from an appropriate managing unit, storing unit, or the
like that manages the packet error rate P. The radio base station
12 refers to the service data information table 421 and reads out
the number of service data packet N and the coefficient C.sub.3
corresponding to the service data number. The radio base station 12
refers to the number of area terminal table 423 and reads out the
number of terminals M corresponding to the area.
[0128] Subsequently, the radio base station 12 calculates a minimum
integer satisfying Expression 6 and sets the minimum integer as the
number of times of multicast transmission. The radio base station
12 stores the number of times of multicast transmission calculated
in the number of multicast transmission table 422 in association
with the area. The radio base station 12 repeats the processing
described above to calculate the number of times of multicast
transmission for all the areas.
[0129] In this embodiment, it is possible to identify any one of
the first to the third determining methods according to the number
of times of multicast transmission determining method ID and
determine the number of times of transmission according to the
method identified. Besides, for example, one appropriate
determining method may be used or a method may be selected from
appropriate two methods of the first to the third determining
methods. Further, rather than the radio base station 12, other
appropriate devices may determine the number of times of multicast
transmission.
[0130] Finally, in this embodiment, as an example, it is assumed
that it is determined to perform multicast transmission three times
in the area 1b, twice in the area 1c, and once in the area 2a. The
radio base station 12 transmits, in multicast, a number of times of
multicast transmission notice including the number of times of
multicast transmission for each of the areas determined to the
radio terminals 20 belonging to the area (step 207). The radio base
stations 12-1 and 12-2 notify the PDSN 14 of a maximum number of
multicast transmission notice including a largest number of
multicast transmission among the numbers of times of multicast
transmission determined earlier for the three areas of the radio
base stations 12-1 and 12-2 (step 208). The maximum number of times
of multicast transmission notice includes a service data number and
the maximum number of times of multicast transmission. In this
embodiment, as the maximum number of times of transmission, the
radio base station 12-1 notifies 3 (times) and the radio base
station 12-2 notifies 1 (time).
[0131] When the PDSN 14 receives the maximum number of times of
multicast transmission notice, the PDSN 14 stores an ID of a radio
base station that transmits the notice and the maximum number of
times of multicast transmission included in the notice in the
multicast information table 661 in the multicast information
storing unit 66. For example, the PDSN 14 stores the ID and the
maximum number of times of multicast transmission in association
with the service data number. The PDSN 14 transmits a PDSN service
data information request to the broadcast download service control
device 15 (step 209). The PDSN service data information request
includes the service data number included in the maximum number of
times of multicast transmission notice (step 208). When the
broadcast download service control device 15 receives the PDSN
service data information request, the broadcast download service
control device 15 transmits PDSN service data information to the
PDSN 14 (step 210). The PDSN service data information includes a
PDSN service data transmission start time and synchronization
information corresponding to the service data number included in
the PDSN service data information request (step 209). The broadcast
download service control device 15 can acquire these pieces of
information with reference to the service information table
711.
[0132] When the PDSN 14 receives the PDSN service data information,
the PDSN 14 stores the PDSN service data transmission start time
and the synchronization information included in the information in
the multicast information table 661 and transmits a service data
request to the data server 16 (step 211). The service data request
includes, for example, the service data number included in the
maximum number of times of multicast transmission (step 208). When
the data server 16 receives the service data request, the data
server 16 transmits service data corresponding to the service data
number included in the service data request (step 211) to the PDSN
14 (step 212). The PDSN 14 stores the service data received from
the data server 16 in the service data storing unit 67.
[0133] When the PDSN service data transmission start time included
in the PDSN service data information comes (or the PDSN service
data transmission start time stored in the multicast information
table comes), the PDSN 14 transmits, in multicast, the service data
to the radio base station 12 stored in the multicast information
storing unit 66 the maximum number of times of multicast
transmission (steps 213, 215, and 217). In other words, the PDSN 14
transmits the service data to the radio base station 12-1 in
multicast three times and to the radio base station 12-2 once.
[0134] The radio base station 12 holds service data arrived before
the service start time in the service information temporarily
storing unit 406 and, when the service start time stored in the
service data information table 421 comes, transmits the service
data. The radio base station 12 transmits the service data to the
designated service areas in multicast the determined numbers of
times (steps 214, 216, and 218). In other words, the radio base
station 12-1 acquires the numbers of times of the respective areas
from the number of times of multicast transmission table 422-1 and
transmits the service data to the area 1b three times and to the
area 1c twice. The radio base station 12-2 transmits the service
data to the area 2a once.
[0135] When the broadcast download service is started, the radio
terminal 20 receives the service data the number of times of
multicast transmission stored in the number of times of multicast
transmission storing unit 37. The radio terminal 20 may decrypt the
service data using the decryption key stored in the decryption key
storing unit 35. It is possible to abandon packets received
redundantly during the reception. After receiving information in
multicast the designated number of times, the radio terminal 20
judges whether any packet could not be received on a basis of, for
example, sequence numbers of packets and, if there is a packet that
could not be received, makes connection to the PDSN 14 in unicast
(step 219). The radio terminal 20 requests the PDSN 14 to
retransmit the packet that could not be received (step 220). The
request includes, for example, a sequence number of the packet
requested to be retransmitted. The radio terminal 20 may judge a
lack of data on a basis of appropriate information other than the
sequence number. Other than the PDSN, the radio terminal 20 may
request, for example, the radio base station 12 to retransmit the
packet.
[0136] In this embodiment, for example, the radio terminals 22a-1
to 22a-1 in the area 2a perform the processing described above
after the reception of multicast data in step 214. The radio
terminals 21c-1 to 21c-k in the area 1c perform the processing
after the reception of multicast data in step 216. The radio
terminals 21b-1 to 21b-j in the area 1b perform the processing
after the reception of multicast data in step 218.
[0137] The PDSN 14 retransmits the requested packet in unicast to
the respective radio terminals (slave stations) 20, which request
retransmission of the packet, using the service data stored in the
service data storing unit 67 (step 221). After that, the respective
radio terminals 20 continue to receive retransmission in unicast
from the PDSN 14 until the service data is completely received
(steps 222 and 223).
[0138] According to the invention, it is possible to surely
transmit information to all the slave stations. When the number of
times of multicast transmission is set to be the number of times
same as that in JP-A-2003-273925, it is possible to complete
transmission early. For example, when time required for delivery
confirmation is set as T.sub.a and the number of times of multicast
is set as x, it is possible to complete transmission early by
xT.sub.a compared with JP-A-2003-273925. It is possible to reduce
consumption of an up transmission capacity during multicast to
zero. Moreover, whereas delivery confirmation information from a
terminal that receives a packet is used in JP-A-2003-273925, in the
present invention, since a retransmission request from a terminal
that could not receive a packet is used, it is possible to control
consumption of an up transmission capacity after multicast is
switched to unicast.
[0139] In this embodiment, the PDSN 14 is set as a retransmission
request destination and a storage is provided in the PDSN 14.
However, it is also possible that the data server 16 is selected as
a retransmission destination or a storage is provided in the radio
base station 12 and the radio base station 12 is set as a
retransmission request destination. The processing for determining
the number of times of multicast transmission may be executed by
the PDSN 14 other than the radio base station 12.
[0140] It is possible to use the invention in, for example,
industries related to communication system and communication
services for transmitting same information to plural terminals.
[0141] According to the invention, it is possible to provide an
information transmitting method and an information transmitting
system for performing transmission surely and quickly without
wastefully consuming a transmission capacity in broadcast download.
According to the invention it is possible to control an up
transmission capacity and reduce the number of times of multicast
transmission as much as possible. According to the invention, it is
possible to reduce time required for surely transmitting
information. Moreover, according to the invention, it is possible
to provide a method of determining the number of times of multicast
transmission.
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